1. Field of the invention
The present invention relates to refrigerating apparatus, more particularly is suitable for use in refrigerating apparatus having a plurality of evaporators in a single refrigeration cycle.
2. Description of the Related Art
There are already refrigerating apparatus containing a plurality of evaporators in a single refrigeration cycle. In such refrigerating apparatus, there is actually no need to constantly supply refrigerant to all evaporators. Instead, it is sufficient to supply the refrigerant to only the necessary evaporators. As a result, generally speaking, the equipment is constructed by installing a solenoid valve in each of the refrigerant tubes leading refrigerant to the evaporators. However, by employing such solenoid valves, the number of parts increases and the number of connection points also increases, thus leading to increased costs.
A technology was proposed that without using solenoid valves refrigerant is stopped being supplied to by forcedly closing expansion valves located upstream of the evaporators. As methods, in Japanese patent application laid-open 57-136074, for example, a technology is disclosed that a cooling element cools a capillary tube communicating to a thermosensitive tube of the expansion valve and the expansion valve is closed to decrease pressure in the thermosensitive tube. Also, in Japanese patent application laid-open 59-38567, a technology is disclosed that a part of a capillary tube communicating with a thermosensitive tube is connected thermally to low-pressure side refrigerant pipe in which low-temperature refrigerant flows at the downstream of the expansion tube, and thermosensitive gas enclosed in a thermosensitive tube is cooled to close the expansion valve and normally the capillary tube is heated by an electric heater.
However, the technology disclosed in Japanese patent application laid-open 57-136074 requires a special cooling element to cool the capillary tube as well as unnecessary electric power to pass a current through that cooling element, thus production cost becomes higher. As for the technology disclosed in Japanese patent application laid-open 59-38567, there is no flow of refrigerant to the low-temperature side refrigerant pipe if the expansion valve is completely closed, which means the capillary tube cannot be cooled. Thus, in order to bring a certain amount of refrigerant to the low-temperature side refrigerant pipe it is not possible to completely close the expansion valve, and since the amount of refrigerant flowing to the low-temperature side refrigerant pipe is small, it is easy to gather compressor oil in the evaporators.
Also, as mentioned above, with the temperature sensitive expansion valve which adjusts the valve aperture by converting the refrigerant pressure of the refrigerant temperature at the exit of the evaporators with the thermosensitive tube. If the high pressure of the refrigeration cycle decreases, the temperature of the expansion valve drops so that the temperature of the expansion valve becomes lower than that of the thermosensitive tube (It is generally known as the "cooling phenomenon"). In such a case, the thermosensitive gas enclosed in the communication space between the thermosensitive tube and the thermosensitive chamber is condensed due to the decline in temperature in the thermosensitive chamber, regardless of the refrigerant temperature at the exit of the evaporators. As a result, the pressure in the thermosensitive chamber (i.e., thermosensitive tube) drops, normal operation is not performed and the valve aperture becomes smaller.